If you have a single entry tourist visa, the stay is 60 days maximum, but again your entry stamp expires when you leave the country (ie single entry). Howeveryou can apply for a re-entry permit when you depart for Vietnam.
It always helps to tell people your nationality when asking questions about visas as the answers depend entirely on your citizenship.
When asking visa/entry requirements, people need to give their nationality
We have both US & Australian citizens traveling in my family. Both countries are exempt.
a maximum of 2 visa exempt entries per year if arriving by land
He never mentioned vietnam visa. He need it
He did "We have both US & Australian citizens traveling in my family. Both countries are exempt."